Method and device for folding an airbag for stowing in an airbag module

ABSTRACT

A method for folding an airbag for an airbag module is characterized in that an empty airbag is spread out and gathered in towards a center to give a folded airbag. The airbag is gathered inside a fixed vertical profiled section having a top and a bottom separated by a distance corresponding to the predetermined height of the folded airbag. Only a few gathering tools and only a few operations are necessary to gather the airbag. A device for carrying out the method is characterized by a lower part on which the airbag is spread out flat and an upper part separated from the lower part by a distance that corresponds to the vertical profile required for the gathered airbag. Gathering tools are mounted between the upper part and the lower part so that they surround the airbag and so that their position relative to the airbag can be changed.

DESCRIPTION

The invention relates to a method for folding an airbag for an airbagmodule according to the preamble of claim 1 and to a device for carryingout the method.

In order to be able to stow an airbag in an airbag module it is known tofold the airbag into a suitably small packet. Various ways of foldingare known. From U.S. Pat. No. 4,173,356 for example different types ofstraight-line folding are known where the folds run in rays out from acentre or approximately parallel to each other. These types of foldinghave the drawback that they have to be gathered together at least whenused for a vehicle airbag module so that when the airbag of this kindunfolds the internal pressure produced in some areas of the airbagprevents the opening of some folds. Furthermore the expense in foldingis considerable.

From DE 44 22 276 A1 an airbag is known for an airbag module where theairbag has main folds which run at least in one part along closed pathsround an imaginary centre on the substantially empty spread-out airbag.The closed main folds preferably describe circular paths or ellipses ofslight eccentricity.

This path of the main folds has the advantage that the folded airbag canopen very rapidly and quickly. More particularly during unfolding ofsuch an airbag there is not the danger that the internal pressureproduced in some area parts of the airbag will prevent the opening offurther folds. This airbag can thereby be used for driver, passenger andside airbags. The drawback with this type of folding is that the expensefor machine folding is high.

The object of the invention is therefore to reduce the expense ofgathering an airbag into a size which allows storage in an airbag modulewhilst ensuring that easy complete unfolding of the airbag in the eventof a crash is guaranteed.

This is achieved according to the invention through the characterisingfeatures of claim 1.

The method for folding the airbag is characterised according to theinvention in that the spread-out empty airbag is gathered towards thecentre inside a fixed vertical profiled section. As opposed to othertypes of folding known up until now with this method a chaotic foldingis undertaken, i.e. the folds have no predetermined shape and direction.It was found however that this folding is substantially free of rear cutsections since the upper part of the airbag always remains at the top.Opening of all the folds is thereby guaranteed during the unfoldingprocess of the airbag.

The gathering process can be carried out from all sides evenly withinthe predetermined height. With an asymmetric airbag module it is howeverexpedient that the airbag is gathered in one direction and then in thedirection at right angles to this alternately until the required size isreached. Gathering is thereby first undertaken at the sides where thereis little space for storing the airbag in the airbag module.

The advantage of this process is that only a few gathering elements arerequired for gathering the airbag and that compared with known foldingprocesses substantially fewer work steps are required. All airbagembodiments can be folded eg with arrester straps and rip seams.

The expense of folding the airbag is only increased by an insignificantamount if according to a further design of the invention a desiredfolding position and bending direction of the airbag fabric is imprintedin the spread-out empty airbag prior to gathering. This can be achievedif prior to gathering the spread-out empty airbag is pre-folded foldedby mechanical forming elements and/or through heat, steam, pressure orvacuum action.

In a preferred embodiment of the method it is proposed to pleat thespread out empty airbag prior to gathering.

It is expedient if the inflating device or a simulator of the inflatingdevice which keeps a space free for the inflating device which is to beinstalled later, is positioned and pre-fitted in the spread-out airbagbefore the latter is gathered.

A device for carrying out the method indicated above is characterised inthat a lower part is provided for holding the spread out airbag and anupper part is provided at distances from the lower part so that thedistances correspond to the vertical profiled section of the gatheredairbag which is required, and that gathering elements are providedbetween the upper part and lower part which enclose the airbag and whoseposition can be changed relative to same. The upper and lower part aredisplaceable relative to each other. The spread out empty airbag for thegathering process is placed on the lower part and the upper part is thenpositioned at the required height above the lower part. The gatheringelements are then pushed against the airbag until this has the requiredshape and size necessary for installation in the airbag module.

For gathering the airbag preferably four gathering elements are providedof which each two oppose each other in pairs wherein the pairs liecross-wise relative to each other. With this arrangement it is reachedthat the airbag is enclosed by the gathering elements around its entirecircumference.

The upper part is preferably formed multi-part by providing a segmentwhich is designed as a holding-down element which has the shape and sizeof the gathered airbag and can be moved separately. By means of thisholding down element it is possible to bring the gathered airbag in thegathering device also into the airbag module or into the generatorplate.

Furthermore it is expedient to also make the lower part multi-part byproviding a segment which is designed as a generator support plateholder which can be moved separately through a cut-out section in alower plate and also by providing sliders which can slide on the lowerplate and enclose at least in part screws of the gas generator as wellas holding rods for the generator support plate holder. This dividedlower part allows the gathered airbag to be fitted into the generatorsupport plate together with the aforementioned divided upper part.

In a further embodiment at least one tension band can be provided as thegathering element.

To predetermine a creasing or bending direction of the airbag throughbores are provided in the upper and/or lower part which can be attachedto a compressed air or vacuum generator. In the area of the throughbores the airbag can be pressed away from the upper or lower part priorto gathering through the incoming compressed air or can be sucked in bythe upper or lower part as a result of a vacuum.

DESCRIPTION OF THE DRAWINGS

In a further embodiment movable pins are provided in the upper and/orlower part to move relative to the airbag to provide a bending orcreasing direction for the airbag.

In another embodiment it is proposed to complete the gathering device bya pleating device by means of which the airbag can be pre-folded.

As a pleating device two ironing plates can be provided each with amatching surface structure which corresponds to the proposed foldingpath. Pleating wheels can also be provided.

This prefolding can be preserved or reinforced by cold and dampness.

The invention will now be explained with reference to the embodimentsshown in the drawings in which:

FIG. 1 shows a cross-section through a gathering device in the startingposition:

FIG. 2 shows two sliders in plan view which are a component part of thelower part of the gathering device;

FIG. 3 shows the position of the gathering device according to FIG. 1after the gathering process;

FIG. 4 shows the position of the gathering device according to FIG. 1when introducing the gathered airbag into a generator support plate;

FIG. 5 is a cross-sectional view through a gathered airbag without priorshaping or provision of the bending or creasing direction;

FIGS. 6a-6c are plan views of the gathering elements before and aftergathering as well as during gathering;

FIG. 7 shows the gathering device with additional openings in the upperand lower parts for introducing compressed air;

FIG. 8 shows the gathering device with additional openings forconnecting to a vacuum generator;

FIG. 9 shows the gathering device with additional pins in the upper andlower parts;

FIG. 10 shows diagrammatically the construction of a pleating device;

FIG. 11 shows the path of the folds provided in the airbag;

FIG. 12 shows a partial sectional view through a folded airbag in agathering device with tension band;

FIG. 13 shows a plan view of FIG. 12;

FIG. 14 shows a plan view on an unfolded airbag in a gathering devicewith tension band;

FIG. 15 shows a section through ironing plates with the airbag inbetweenprior to prefolding;

FIG. 16 shows a section through the airbag after pre-shaping by means ofthe ironing plates according to FIG. 15.

The gathering device consists of an upper part 1 and a lower part 2. Theupper part 1 has an upper plate 3 and a holding down member 4 in anopening of this plate. The lower part 2 consists of a lower plate 5 onwhich two sliders 6,7 are mounted movable relative to each other. As canbe seen from FIG. 2 the sliders meet each other in the position of FIG.1 with straight parallel edges 8 and thereby enclose with rounded edgesections 10, 11 a gas generator 9 as well as screws 12 of the gasgenerator 9 and retaining rods 13 for the gas generator. A generatorsupport plate 15 is mounted underneath the sliders 6,7 in a holder 14.The holder 14 can be displaced upwards through a recess in the lowerplate 5.

An airbag 16 is located in the spread out empty state on the sliders 6,7between gathering elements 1720 (FIG. 6) of which only two are shown inFIG. 1.

In order to carry out the gathering of the airbag 16 the upper part 1 isfirst lowered until the distance h (FIG. 3) between the upper part 1 andlower part 2 corresponds to the proposed height of the folded airbag. Inthis position the airbag 16 is fixed firm on the gas generator 9 by theholding down member 4. The gathering elements 17 to 20 enclose thespread-out airbag 16 (FIG. 6a) and fit with slight play between theupper and lower part.

For gathering, the gathering elements are moved in the direction of thecentre of the airbag. The gathering elements can thereby be pushedsimultaneously or in succession. In FIGS. 6b and 6c the case is shownwhere first the gathering elements 19,20 are moved towards the centre.The gathering shown in FIG. 6b is thereby produced where the airbagbecomes smaller in the direction of the gathering whilst it expands inthe direction running crosswise relative to same.

At the end of gathering by means of the gathering elements 19, 20,gathering is undertaken crosswise relative to same by means of thegathering elements 17,18. The airbag thereby forms naturally into foldsduring the gathering process and is restricted top and bottom by theupper and lower parts.

The gathering process is completed when the airbag is compressed to sucha size that it can be inserted in the airbag module. The generatorsupport plate 15 belongs here into which the gathered airbag is to beinserted. To this end the holder 14 with generator support plate 15 ispushed up to the underneath of the sliders 6,7. The sliders 6,7 are thenremoved from the area of the airbag 16 and the gathered airbag 16 ispushed by means of the holding down member 4 together with the gasgenerator 9 into the generator support plate (FIG. 4).

It can be seen from the path of the folds shown in FIG. 5 that the foldshave no preferred direction. Tests have shown however that with thisnatural folding the upper part of the airbag always lies at the top sothat folding takes place substantially without rear cut sections. Easyunfolding of the entire airbag is thereby ensured.

Without a great multiple expense it is also possible to predefine thecreasing and bending direction of the airbag. To this end in theembodiment of FIG. 7 through bores 21 are provided in the upper part 1and through bores 22 are provided in the lower part 2 so that compressedair can be blown in through same into the space formed by the upper andlower parts 1,2 and the gathering elements 17 to 20. The spread outairbag 16 is pressed onto the lower part 1 through the compressed air ofthe through bores 21 whilst the airbag is lifted up by the compressedair to the through bores 22 so that the bending and creasing directionis predetermined. The biasing with compressed air can remain throughoutthe gathering process since no mechanical parts engage in the spacebetween the upper and lower part.

In the embodiment of FIG. 8 through bores 23 are provided in the upperpart 1 and through bores 24 are provided in the lower part 2 which areattached to a vacuum pump (not shown). As a result of the vacuum theairbag is sucked against the lower part in the area of the through bores24 whilst it is lifted in the area of the through bores 23. Thus as withthe embodiment of FIG. 7 the creasing and bending direction is therebypredetermined.

In the embodiment of FIG. 9 the upper part 1 has pins 32 of which onlyone is shown. Furthermore the lower part 2 has pins 33. These pins aremounted movable in the upper pat and lower part so that the pins of onepart lie between the pins of each other part. If the pins are movedtowards each other the airbag is pre-folded through the pins as shown inFIG. 9. During the gathering process as the gathering elements drawnearer so the pins 32, 33 are drawn back stepwise from the space betweenthe upper part 1 and lower part 2 so that the airbag is brought by thegathering device to the size required for installation in the airbagmodule.

In the embodiment of FIG. 10 a pleating device is shown in diagrammaticform. This has pleating wheels 25 with a positive profile 27 on thecircumference and counter wheels 26 with a negative profile 28. Thepleating wheels with the positive and negative profiles mesh with eachother so that the airbag 16 to be pleated is located between same.

The position of the axes relative to each other depends on the desiredalignment of the folds. In the embodiment of FIG. 10 the folds are torun along circular paths as shown in FIG. 11. Therefore on each side ofthe airbag to be pleated pleating wheels of different size are mountedon shafts whose longitudinal axes 29, 30 run through a point 31.

The embodiment of FIGS. 12, 13 and 14 shows the gathering processperformed by means of a tension band 34. This is associated with tensionband jaws 35 which hold the tension band in its starting position bymeans of cylinders 36. The tension band 34 is drawn from this by meansof a pressure cylinder 37 wherein the tension band jaws 35 therebychange their position as well until they adjoin an adjustable stop baseplate 38 as shown in FIGS. 12 and 13. The tension band jaws 35 determinethe outer shape of the gathered airbag since the tension band is bentdown on each jaw 35. The direction of movement of the tension band jawsis shown by arrows in FIG. 14.

As can be seen from FIG. 14 the band ends run over guide pulleys 39 andare fixed on a cross bar 40 which is seated on the piston rod of thepressure cylinder 37. The airbag is shown in FIGS. 12 and 13 in thefolded state whilst in FIG. 14 it is shown spread out between thetension bands prior to the start of folding.

The structure shown in FIGS. 11 and 16 can also be achieved by means oftwo ironing plates 41, 42 with matching surface structure. The foldedposition and direction of the folds are set in the airbag by steam andheat by means of these plates.

What is claimed is:
 1. Method for folding an empty airbag for an airbagmodule to produce a folded airbag having a center and a predeterminedheight, the method comprising:spreading out the empty airbag; providinga fixed vertical profiled section having a top surface and a bottomsurface separated by a distance corresponding to the predeterminedheight of the folded airbag with the airbag with gathering elementsmoving located between the top surface and the bottom surface; andthereafter gathering up the spread out empty airbag towards the centerinside the fixed vertical profiled section in a direction generallyparallel to the top and bottom surfaces thereby forming a plurality offolds in the airbag.
 2. Method according to claim 1, wherein thegathering step comprises gathering the airbag first in one direction andthen in a direction perpendicular thereto down to a required size. 3.Method according to claim 1 further comprising the step of:imprinting onthe spread out empty airbag, before the gathering step, a desired foldposition and bending direction of an airbag fabric.
 4. Method accordingto claim 1 further comprising the step of:pre-folding the spread outempty airbag, prior to the gathering step, through mechanical shapingelements or through heat, steam, pressure or vacuum action or throughany combination thereof.
 5. Method according to claim 1 furthercomprising the step of:pleating the spread out empty airbag prior to thegathering step.
 6. Method according to claim 1 further comprising thestep of:positioning an air inflating device in the spread out airbagbefore the gathering step.
 7. Device for folding an airbag to provide agathered airbag having a predetermined vertical profile, comprising:alower part for holding a spread out airbag, an upper part distanced fromthe lower part to form a fixed vertical profile section corresponding tothe predetermined vertical profile of the gathered airbag, and gatheringelements between the upper part and lower part, wherein the gatheringelements have an inner surface to contact the airbag and the position ofthe gathering elements can be moved in a direction generally parallel tothe upper part and lower part, whereby, during operation, the innersurfaces of the gathering elements contact and enclose the airbag as theairbag is gathered.
 8. Device according to claim 7 wherein the gatheringelements comprise four gathering elements,wherein each two gatheringelements are opposite each other in pairs, and wherein the pairs ofgathering elements lie crosswise relative to each other.
 9. Deviceaccording to claim 7 wherein the upper part is multi-part,wherein aseparately movable segment is provided, wherein the separately movablesegment is designed as a holding down holder, and wherein the separatelymovable segment has a size of the gathered airbag.
 10. Device accordingto claim 7 wherein the lower part is multi-part and further comprises,asegment designed as a generator support plate holder wherein the segmentcan be moved separately through a cut out section in a lower plates, andwherein sliders are provided, and wherein the sliders are displaceableon the lower plate to encloses, at least in part screws of a gasgenerator as well as holding rods for the generator support plateholder.
 11. Device according to claim 7 wherein the upper part or thelower part comprises through bores.
 12. Device according to claim 7wherein the gathering element comprise at least one tension band. 13.Device according to claim 7 wherein the upper part or lower partcontains pins, andwherein the pins can be moved relative to the airbagto pre-shape a creasing and folding direction of the airbag.
 14. Deviceaccording to claim 7 further comprising a pleating device.
 15. Deviceaccording to claim 14 wherein the pleating device further comprises twoironing plates, andwherein the ironing plates comprise matching surfacestructures corresponding to a proposed folding path.
 16. Deviceaccording to claim 14 wherein the pleating device further comprisespleating wheels.
 17. Device according to claim 11 wherein the throughbores are attached to a compressed air generator.
 18. Device accordingto claim 11 wherein the through bores are attached to a vacuumgenerator.
 19. Method according to claim 1 wherein the plurality offolds of the airbag have no predetermined shape or direction.
 20. Methodaccording to claim 1 wherein the spread out empty airbag is flat at thebeginning of the gathering step.
 21. Method according to claim 1 whereinthe gathering step includes gathering the airbag inside the fixedvertical profiled section using a plurality gathering elements, eachhaving an inner surface in contact with the airbag, and further whereinthe inner surface of each gathering element does not overlap with theinner surface of any other gathering element.
 22. Device according toclaim 7 wherein the gathering elements each have an inner surface incontact with the airbag, and further wherein the inner surface of eachgathering element does not overlap with the inner surface of any othergathering element.
 23. Method according to claim 1 wherein the gatheringstep includes gathering the airbag inside the fixed vertical profiledsection using a plurality gathering elements, each having a generallyflat inner surface in contact with the airbag.
 24. Device according toclaim 7 wherein the gathering elements each have a generally flat innersurface in contact with the airbag.
 25. Method according to claim 1,farther comprising including a gas generator at a center of the spreadout airbag within the fixed vertical profile section, wherein thegathering step includes gathering the airbag inside the fixed verticalprofiled section by moving a plurality gathering elements in alignmentwith the gas generator.
 26. Method according to claim 1, wherein themethod for folding is performed without inflating the airbag.
 27. Amethod according to claim 1, wherein the top surface overlies the entirespread out airbag.
 28. A method according to claim 27, comprisingvertically moving at least a portion of the upper surface in concertwith at least a portion of the bottom surface with the folded airbagtherebetween.
 29. An apparatus according to claim 7, wherein the upperpart overlies the entire spread out airbag.
 30. An apparatus accordingto claim 29, wherein at least a portion of the upper part is verticallymoveable in concert with at least a portion of the lower part.
 31. Amethod according to claim 1, wherein the vertical profiled section isprovided by vertically lowering the top surface toward the bottomsurface.
 32. An apparatus according to claim 7, wherein the upper partis in a first position when it is distanced from the lower part to formthe fixed vertical profiled section, and further wherein the upper partis vertically moveable between the first position and a second positionabove the first position.
 33. Method for folding an empty airbag for anairbag module to produce a folded airbag having a center and apredetermined height, the method comprising:spreading out the emptyairbag; providing a fixed vertical profiled section having a top surfaceand a bottom surface separated by a distance substantially correspondingto the predetermined height of the folded airbag; and gathering up thespread out empty airbag towards the center with gathering elementsinside the fixed vertical profiled section in a direction generallyparallel to the top surface and the bottom surface wherein the gatheringelements each have a height corresponding to the predetermined heightsubstantially of the folded airbag, thereby forming a plurality of foldsin the airbag.
 34. Device for folding an airbag to provide a gatheredairbag having a predetermined vertical profile, comprising:a lower partfor holding a spread out airbag, an upper part distanced from the lowerpart to form a fixed vertical profile section corresponding to thepredetermined vertical profile of the gathered airbag, and gatheringelements between the upper part and lower part, wherein the gatheringelements enclose the airbag and can be moved in a direction generallyparallel to the upper part and lower part, and further wherein thegathering elements each have a height substantially corresponding to thepredetermined height of the folded airbag.
 35. Method for folding anempty airbag for an airbag module to produce a folded airbag having acenter and a predetermined height, the method comprising:spreading outthe empty airbag; providing a fixed vertical profiled section having atop surface and a bottom surface separated by a distance substantiallycorresponding to the predetermined height of the folded airbag; andgathering up the spread out empty airbag with gathering elements movingtowards the center inside the fixed vertical profiled section in adirection generally parallel to the top and bottom surfaces, wherein thegathering elements have inner surfaces that contact and enclose theairbag as the airbag is gathered, thereby forming a plurality of foldsin the airbag.
 36. An airbag folding apparatus for producing a foldedairbag having a top, the apparatus including:a loading portion to permita flatly spread airbag having a center to be place thereon; a pushingmeans for pushing the peripheral edge of the airbag toward the center;and a height restricting means for restricting the distance between thetop of folded airbag and the loading portion.